The present invention relates to air separation systems which function to separate nitrogen which may then be used to inert an open space such as a fuel tank or cargo hold of an airplane.
Hollow fiber membranes, which constitute the air separation media for air separation systems, are housed in Air Separation Canisters. These canisters are used in air separation systems to generate nitrogen enriched air (NEA) and oxygen enriched air (OEA). The performance of these canisters, in terms of NEA generation rate and purity, is sensitive to the operating pressure and temperature of the inlet air flow. In addition, the performance is affected by the thermal conditions of the surrounding environment, to the extent that performance degrades significantly as the surrounding temperature falls below an effective operating range of temperatures. A separate thermal conditioning system could be added to canisters to heat them with electric resistance heaters or hot bleed air. However, the electric power system capacity is limited in applications such as aircraft fuel tank inerting systems. In addition, the bleed air supply system capacity is limited in aircraft applications, and does not have excess flow to be utilized for additional thermal conditioning applications.
There therefore remains a need for an efficient method and apparatus for thermally conditioning and controlling the temperature of the air space in which the air separation canisters are located to optimize the performance thereof.